The present invention relates to environmentally degradable articles, films, bags together with containers fabricated from the degradable polymeric compositions including polyester, polyamide, polystyrene and polyvinyl chloride compositions.
A wide variety of environmentally degradable polymeric compositions have been used for the fabrication of containers, films, bags and the like in the past. Many have required chemical modification of the polymers and are difficult to work with and expensive. Many of these polymeric compositions required the use of photosensitive additives to a host polymer to impart environmental degradability to the articles, particularly by photodegradation mechanisms. The use of such additive systems has caused subtantial problems in the past. For example, such polymer-photosensitive additive systems have exhibited spontaneous separation of the components or component migration to surface of the article during and after melt extrusion. Further, such additive systems are often subject to discoloration or odor generation during processing of the melt. This requires the addition of dye colorants to maintain an acceptable product appearance. Further, such systems have had poor extrusion viscosity characteristics and poor thermoformability and have not exhibited the requisite stiffness or flexibility for certain applications.
In the past, a blended material of high density polyethylene or medium density polyethylene admixed with an ethylene-carbon monoxide copolymer in the concentrations of 3-50 percent ethylene-carbon monoxide copolymer, wherein the mixture contains about 0.1 to about 15 weight percent of carbon monoxide has been used for various articles. Such a degradable polyethylene ethylene-carbon monoxide copolymer material is described in German Patent document 2316697 entitled "Polymeric Substance Photo-Decomposable By the Action of Ultraviolet Irradiation."
The material disclosed in German patent document 2316697 is limited to high density polyethylene and medium density polyethylene having between 3-50 percent ethylene-carbon monoxide copolymer and discloses the use of copolymers of ethylene-propylene, ethylene-butene, ethylene-vinylacetate, ethylene-styrene, ethylene-methylacrylate and ethylene-hexene copolymers in the place of polyethylene. The polyethylene-ethylene-carbon monoxide blended materials disclosed in the 2316697 document degrades too rapidly for successful use in articles requiring flexibility. The 2316697 document has no suggestion of polyesters, polyamides, polystyrene and polyvinyl chloride. Accordingly, there exists a need in the art for environmentally degradable polymeric compositions (comprising polyesters, polyamides, polystyrene and polyvinyl chloride) having sufficient mechanical properties for use as an article which exhibits balanced environmental degradation, excellent mechanical properties, extrudability, thermoformability and does not spontaneously suffer component migration or separation upon melt extrusion formation or during use.
U.S. Pat. Nos. 4,709,808 and 4,714,741 of Jabarin and Balduff, assigned to Owens-Illinois, Inc., disclose degradable compositions and articles, the compositions having high density polyethylene, low density polyethylene and polypropylene plus a CO-containing polymer.
There is no suggestion in these patents of how to easily and economically prepare degradable polyesters, polyamides, polystyrenes or polyvinyl chloride.